Shock absorber for swivel caster

Abstract

A device for use with a bearing construction for a swivel caster mountable on a caster mounting plate and including a yoke having a swivel plate pivotal about a pivot axis. A securing device is provided for securing the yoke to the caster mounting plate. The bearing construction is composed of a ball bearing retaining structure which normally abuts against the underside of the caster mounting plate. An elastomeric member is mounted between the bearing construction and the caster mounting plate. The elastomeric member has a compressible characteristic sufficient to maintain the caster firmly connected to the mounting plate while simultaneously being capable of yielding to a sufficiently large force applied to the yoke to permit a relative movement between the mounting plate and the yoke to thereby prevent permanent deformation to the yoke when an abnormally high force is applied thereto. The securing device includes structure for limiting the initial compression of the elastomeric member between the bearing construction and the mounting plate.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. In a device for use with a bearing construction for a caster mountable on a caster mounting plate including a yoke and securing means for securing said yoke to said caster mounting plate, wherein said securing means includes pin means rigidly secured to and coaxial with said bearing construction, the axes of said pin means and said bearing construction extending in a normal position perpendicular to said caster mounting plate through an opening therein, the improvement comprising first means for facilitating a tilting of said axes relative to said mounting plate, an elastomeric member mounted between said bearing construction and said caster mounting plate, said elastomeric member having a compressible characteristic sufficient to maintain said caster firmly connected to said mounting plate to maintain said axes in said normal position while simultaneously being capable of yielding to a sufficiently large force applied to said yoke to permit a relative movement between said mounting plate and said yoke to thereby prevent permanent deformation to said yoke when an abnormally high force is applied thereto and wherein said securing means includes second means for limiting the initial preload of said elastomeric member between said bearing construction and said mounting plate to maintain said axes in said normal position while simultaneously facilitating a relative tilting movement of said axes relative to said mounting plate, said elastomeric member effecting a return of said axes to said normal position. 
     
     
       2. The improved device according to claim 1, wherein said yoke includes a swivel plate; and wherein said bearing construction includes bearing ball retaining means comprising first and second, annular bearing ball retainers disposed upon opposite sides of and spaced from said swivel plate and a plurality of bearing balls disposed between said ball retainers on opposite sides of said swivel plate for snug rolling engagement with said ball retainers and said swivel plate; and   wherein said elastomeric member is located between one of said bearing ball retaining means and said mounting plate.   
     
     
       3. The improved device according to claim 2, wherein said elastomeric member has an annular wall portion between said one of said bearing ball retaining means and said mounting plate, said annular portion including an annular bead of elastomeric material which is thicker than the remainder thereof and is located adjacent the peripheral edge thereof, said thicker part being compressed and yielding to said sufficiently large force. 
     
     
       4. The improved device according to claim 3, wherein said elastomeric member is cup-shaped having an outwardly tapered wall extending away from the peripheral edge of said annular wall portion to fit around said one of said annular bearing ball retainers and including a lip portion frictionally engaging said swivel plate with sufficient friction to permit a normal pivoting of said swivel plate and yoke while simultaneously preventing a rapid back-and-forth pivoting of said swivel plate and yoke and sealing the bearing balls from outside contaminants. 
     
     
       5. The improved device according to claim 2, wherein said bearing ball retaining means includes spacing means sleeved upon said pin means and extends between said ball retainers near their radially inner edges to limit movement of said ball retainers toward each other; wherein said opening through said mounting plate has a diameter substantially smaller than the diameter of said pin means to define a spacing therebetween which is greater than a normal clearance spacing;   wherein said means for limiting the initial preload of said elastomeric member includes an annular groove in said pin means on a side of said mounting plate opposite said bearing ball retaining means and annular spring washer means including third means received in said annular groove and fourth means engaging said mounting plate, said spring washer means urging said pin means into tight engagement with said bearing ball retaining means to snugly clamp said elastomeric member in place while simultaneously permitting said relative tilting movement between said pin means and said mounting plate.   
     
     
       6. The improved device according to claim 5, wherein said elastomeric member includes a sleeve portion snugly encircling said pin means and snugly received in said spacing to resiliently maintain said pin means in a central relationship in said opening while simultaneously yielding to various forces applied to said yoke. 
     
     
       7. The improved device according to claim 6, including an elastomeric washer resiliently clamped between said fourth means and said mounting plate. 
     
     
       8. The improved device according to claim 2, wherein said bearing ball retaining means includes spacing means sleeved upon said pin means and extends between said ball retainers near their radially inner edges to limit movement of said ball retainers toward each other; where said opening through said mounting plate has a diameter substantially smaller than the diameter of said pin means to define a spacing therebetween which is greater than a normal clearance spacing;   wherein said means for limiting the initial preload of said elastomeric member includes a shoulder on said pin means on a side of said mounting plate opposite said bearing ball retaining means spaced from said one of said bearing ball retainer means a predefined distance, a thread on said pin means on the free end thereof extending to said shoulder and a nut threaded on said thread and snugly engaging said shoulder and further including an elastomeric washer resiliently clamped between said nut and said mounting plate to facilitate the movement of said pin means relative to said mounting plate.   
     
     
       9. The improved device according to claim 8, wherein said elastomeric member includes a sleeve portion snugly encircling said pin means and snugly received in said spacing to resiliently maintain said pin means in a central relationship in said opening while simultaneously yielding to various forces applied to said yoke. 
     
     
       10. The improved device according to claim 9, including an elastomeric washer resiliently clamped between said nut and said mounting plate.